Single Threaded Tonic Client/Server

[artsiomkaltovich]

Feature Request

Motivation

Tonic requires Send + Sync for the client code, that make it hard to introduce to single-threaded async code. Not every service should be multi-threaded and now adding tonic in single threaded code could be painful.
This topic was raised several times:

Single threaded server example with async_trait(?Send) (open): https://github.com//issues/2171
how to generate trait with #[async_trait(?Send)] (closed): https://github.com//issues/844
feat: Support thread-local functionality (closed PR): https://github.com//pull/1505
add Single-threaded runtime (closed): https://github.com//issues/784

however, it wasn't fully implemented yet.

Proposal

I think ability to run tonic natively in single-threaded without send+sync addition would benefit the community a lot.

To be honest I haven't check the src yet. There were suggestions to replace async_trait with async_trait(?Send) another approach is code split and introducing local versions for code (with/or without feature flag).

[sauravzg]

Hi, This is not something that we have on our current grpc-rust roadmap or bandwidth to explore/prioritise this.

@LucioFranco It seems like something that's been brought up a few times for tonic. Is this something we want to address?

[artsiomkaltovich]

I've just checking if this is an option or just strict no.

I could try to implement it, however I am not very familiar with a project, so I can't guarantee anything. :)
Any insights welcomed.

[sauravzg]

Feasibility , design, tradeoff analysis and implementation would require some effort, that we currently don't have bandwidth to put into for the near future.